Morpho-physiological response of bedding plants quality to unconventional agro-industrial organic matrices to peat replacing: preliminary outcomes.

Product quality and agro-environmental sustainability are essential for the long-term sustainability of the floriculture industry. Reducing or replacing the use of peat (P) and establishing circular waste flows are crucial steps towards sustainable production of potted plants. Recycling agro-industry by-products represents an important challenge for a circular economy. In this study, ten substrates were investigated for the production of potted French marigold (Tagetes patula) and nasturtium (Tropaeolum minus) bedding plants, and two different plant development stages were considered: transplants and marketable plants. P (85% v:v) was proportionally substituted with stabilized wood fibre (SWF), coffee silverskin (CS) and brewer spent grain (BSG) in ratios of 0, 10, 20, and 40% (v:v). In the ten growing media pumice was always at 15% (v:v). The first results showed that in the case of transplants both SWF and BSG are valid matrices at up to 10 or 20% rate of P replacement in nasturtium and marigold respectively. In marketable plants, both SWF and CS can be used at up to 40% rate; on the contrary BSG, in the mixtures, had a depressive effect on the marigold quality; in nasturtium, SWF at up to 40% gave a higher plant quality than the control. CS and BSG provided a quality performance similar to the control (peat).